Preparation method of high-toughness NDI-based fluorescent polyurea

Abstract

The application belongs to the field of polymer preparation, and particularly relates to a preparation method of high-toughness NDI-based fluorescent polyurea, which uses NDI, polyetheramine, TEPA and IPDI as raw materials, uses the rapid reaction of isocyanate and amino group to enable NDI, polyetheramine and TEPA to construct a main chain under mild conditions, uses the reaction of diisocyanate and secondary amine to enable the main chain to be crosslinked, the difference between hydrogen bond and covalent bond breaking energy forms a gradient energy dissipation mechanism, the toughness of the material is greatly improved, the hydrogen bond and covalent bond crosslinking limit the'movement' of the planar rigid conjugated structure, the non-radiative transition is weakened, the radiative transition is enhanced, and this is conducive to the enhancement of the fluorescent properties. The preparation method of the high-toughness fluorescent polyurea is novel, the prepared polyurea has ultrahigh toughness and fluorescent properties, the raw materials used in the application have low cost, and the application has wide market prospects. The steps are simple, the operation is convenient, and the application has strong practicability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer preparation, and particularly relates to a preparation method of high-toughness NDI (1,5-naphthalene diisocyanate) based fluorescent polyurea. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of generally presenting the context of the application. The information disclosed in this Background section is not to be taken as an acknowledgement or any form of suggestion that this information forms prior art that is already known to a person skilled in the art.

[0003] Polyurea is a kind of high molecular material generated by step-by-step addition reaction of isocyanate component and amino compound component, and no by-product is generated in the reaction process. Polyurea often has good mechanical properties and is widely used in pipeline corrosion protection, surface decoration and other fields. At present, the isocyanate component used in the synthesis of polyurea is usually IPDI (isophorone diisocyanate), HDI (hexamethylene diisocyanate), TDI (toluene diisocyanate) and MDI (diphenylmethane diisocyanate), and the application of NDI (naphthalene diisocyanate) in the field of polyurea is very rare. This is mainly because the melting point of NDI is relatively high, and the temperature must be above 120℃ to carry out the melting reaction, and the reaction between amino and isocyanate is too violent at high temperature to normally polymerize, which leads to the fact that this method cannot be applied in the field of polyurea. However, the highly symmetrical structure and rigidity of NDI make it have good physicochemical properties, and its application in the field of polyurea has a very broad application prospect.

[0004] Cross-linked polyurea material is a three-dimensional network structure polymer formed by chemical cross-linking or physical cross-linking. Due to its unique structure, cross-linked polyurea material usually has high hardness and rigidity, and shows excellent mechanical properties and chemical resistance in many applications. However, this kind of material also has some inherent disadvantages, because of the cross-linking between chains, the chain mobility is reduced, and the toughness is often poor, which limits their wide application in some fields.

[0005] The fluorescence of organic polymer material is mainly caused by the structure of a certain region of molecules in the chain segment or between the chain segments. The photoluminescence performance mainly depends on the conjugated structure, intramolecular and intermolecular interaction, which mainly includes Π-Π interaction, hydrogen bond and halogen bond, etc. Fluorescence can be applied in many fields such as information storage and encryption, information marking and display due to its special luminescent properties. However, the current polyurea products often have difficulty in balancing high toughness and fluorescent properties. SUMMARY

[0006] In order to solve the above problems, the application provides a high-toughness NDI-based fluorescent polyurea and a preparation method thereof. Based on the difference between hydrogen bond and covalent bond breaking energy, gradient energy dissipation is formed to enhance the toughness of the material, a planar rigid conjugated structure (naphthalene ring) is introduced to endow the material with fluorescent properties, the fluorescent intensity of the material can be changed by changing the crosslinking degree of the material and the substituents on the naphthalene ring, and the material has certain response to stretching and acid-base.

[0007] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0008] In a first aspect, the application provides a high-toughness NDI-based fluorescent polyurea, and the structural formula is as follows:

[0009]

[0010] In the formula, n is a natural number greater than zero.

[0011] In the high-toughness NDI-based fluorescent polyurea system of the application, the naphthalene ring contains urea groups as substituents, and when all the substituents in the system are urea groups, the fluorescent intensity is the largest, and when the substituents on the naphthalene ring are urethane groups and all the substituents in the system are urethane bonds, the fluorescent intensity is the smallest.

[0012] In a second aspect, the application provides a preparation method of the high-toughness NDI-based fluorescent polyurea, and the method comprises the following steps:

[0013] The NDI is reacted with polyether amine to obtain an isocyanate-terminated prepolymer;

[0014] TEPA is used to chain-extend the isocyanate-terminated prepolymer, and after the reaction is completed, diisocyanate is added for further reaction.

[0015] Under the action of external force, the gradual rupture of different levels of interaction can greatly dissipate energy, so that the material has excellent toughness. Therefore, the application introduces different levels of hydrogen bonds and covalent bonds in the polyurea network to form gradient energy dissipation, thereby enhancing the toughness of the material. The prepared NDI-based fluorescent polyurea has both mechanical strength and toughness, and can meet the use requirements in different fields.

[0016] In some embodiments, the molar ratio of the NDI to the polyether amine is 1:0.3-1.

[0017] In the reaction in the solvent, when the temperature is higher than 60 DEG C, the NDI can react with water, DMF and the like. Therefore, the high reactivity of the amino group and the isocyanate group is used to enable the reaction to be carried out under relatively mild conditions. Preferably, the temperature for the reaction of the NDI with the polyether amine is 0 DEG C-60 DEG C.

[0018] In some embodiments, the temperature of the chain extension reaction is room temperature.

[0019] In some embodiments, the molar ratio of the polyether amine to TEPA is 1:0.3-1.

[0020] In some embodiments, the reaction temperature of the diisocyanate and the secondary amine is 50-100℃.

[0021] In some embodiments, the molar ratio of the TEPA to diisocyanate is 1:0.3-1.6.

[0022] In some embodiments, the diisocyanate is selected from one of IPDI, HDI, TDI.

[0023] In a third aspect of the present application, the use of the high-toughness NDI-based fluorescent polyurea described above in the field of information storage and encryption, information marking and display is provided.

[0024] Advantages of the present application

[0025] (1) The preparation method of the high-toughness NDI-based fluorescent polyurea described in the present application is novel, mild in conditions, and has a deep research value.

[0026] (2) Based on the gradient energy dissipation mechanism, the present application utilizes the breaking of strong and weak hydrogen bonds and the breaking of side chain covalent bonds in the material to form a gradient energy dissipation, reduces stress concentration, and as the stretching proceeds, the breaking of side chain covalent bonds produces new hydrogen bond donors and acceptors, which is conducive to the rapid recombination of hydrogen bonds, further enhances the energy dissipation mechanism, promotes the slipping and rearrangement of chain segments, and thus endows the material with ultra-high toughness.

[0027] (3) By introducing a planar rigid conjugated structure (naphthalene ring), the present application endows the material with fluorescent properties, limits the "movement" of the naphthalene ring through cross-linking between the main chains, enhances the fluorescent properties of the material, and the acid-base can change the fluorescence intensity of the material. By changing the types of substituents on the naphthalene ring, the fluorescent properties have obvious changes.

[0028] (4) The preparation method of the present application is simple, low in price, strong in practicality, and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the exemplary embodiments of the present application and their description, serve to explain the present application, and do not constitute an improper limitation of the present application.

[0030] Figure 1 Toughness diagram of polyurea with different crosslinking degrees.

[0031] Figure 2 Fluorescence spectrum diagram of polyurea with the same crosslinking degree.

[0032] Figure 3 The fluorescence spectrum of NDI-based fluorescent polyurea at different pH values.

[0033] Figure 4 The fluorescence spectrum of different substituents on the naphthalene ring. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0035] The application will be described in further detail below with reference to specific examples. It should be noted that the specific examples are intended to explain the application, not to limit it.

[0036] In the following examples, the following test methods were used:

[0037] Tensile test was tested according to GB / T 1024.2-2006, with a test speed of 100 mm / min at room temperature.

[0038] The fluorescence spectrum was measured under the same standard.

[0039] Example 1

[0040] DMAC was used as the solvent, 10 g of polyetheramine D-2000 and 1.576 g of NDI were added to a 250 ml three-necked flask, and the reaction was carried out at 50°C under N2 atmosphere until the solid completely disappeared, obtaining a viscous solution as a prepolymer. After cooling to room temperature, 0.473 g of TEPA was dissolved in DMAC and added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the process. The reaction was carried out at room temperature for 3 h. After the reaction was completed, 0.305 g of IPDI was added to the three-necked flask, and the reaction was continued at 65°C for 7 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried into a film at 70°C.

[0041] Example 2

[0042] Into a 250 ml three-necked flask, polyetheramine D-2000 (10 g) and NDI (1.576 g) were added with DMAC as solvent, and the reaction was carried out at 50°C under N2 atmosphere until the solid completely disappeared to obtain a viscous solution, which was a prepolymer. After cooling to room temperature, TEPA (0.473 g) dissolved in DMAC was added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the reaction, and the reaction was carried out at room temperature for 3 h. After the reaction was completed, IPDI (0.611 g) was added to the three-necked flask, and the reaction was continued at 65°C for 7 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried into a film at 70°C.

[0043] Example 3:

[0044] Into a 250 ml three-necked flask, polyetheramine D-2000 (10 g) and NDI (1.576 g) were added with DMAC as solvent, and the reaction was carried out at 50°C under N2 atmosphere until the solid completely disappeared to obtain a viscous solution, which was a prepolymer. After cooling to room temperature, TEPA (0.473 g) dissolved in DMAC was added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the reaction, and the reaction was carried out at room temperature for 3 h. After the reaction was completed, IPDI (0.917 g) was added to the three-necked flask, and the reaction was continued at 65°C for 7 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried into a film at 70°C.

[0045] Example 4:

[0046] Into a 250 ml three-necked flask, polyetheramine D-2000 (10 g) and NDI (1.576 g) were added with DMAC as solvent, and the reaction was carried out at 50°C under N2 atmosphere until the solid completely disappeared to obtain a viscous solution, which was a prepolymer. After cooling to room temperature, TEPA (0.473 g) dissolved in DMAC was added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the reaction, and the reaction was carried out at room temperature for 3 h. After the reaction was completed, IPDI (0.917 g) was added to the three-necked flask, and the reaction was continued at 65°C for 7 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried into a film at 70°C.

[0047] Example 5:

[0048] To a 250 ml three-necked flask, polyetheramine D-2000 (10 g), NDI (1.576 g) were added as solvent DMAC, and the reaction was carried out at 50°C under N2atmosphere until the solid completely disappeared to obtain a viscous solution, which was a prepolymer. After cooling to room temperature, TEPA (0.473 g) was dissolved in DMAC and added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the reaction, and the reaction was carried out at room temperature for 3 h. After the reaction was completed, TDI (0.718 g) was added to the three-necked flask, and the reaction was continued at 65°C for 7 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried at 70°C to form a film.

[0049] Comparative Example 1:

[0050] To a 250 ml three-necked flask, polyetheramine D-2000 (10 g), NDI (1.576 g) were added as solvent DMAC, and the reaction was carried out at 50°C under N2atmosphere until the solid completely disappeared to obtain a viscous solution, which was a prepolymer. After cooling to room temperature, TEPA (0.473 g) was dissolved in DMAC and added to the prepolymer, and solvent was constantly added to dilute and prevent gelation during the reaction, and the reaction was carried out at room temperature for 3 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried at 70°C to form a film.

[0051] Comparative Example 2:

[0052] To a 100 ml three-necked flask, polyetheramine (Mn=2000, 4 g), HDI (0.706 g), DBTDL (0.02 g) were added as solvent DMAC, and the reaction was carried out at 80°C under N2atmosphere for 2 h with mechanical stirring to obtain a colorless viscous solution, which was a prepolymer. After obtaining the prepolymer, 1,5-dihydroxynaphthalene (0.32 g) was added, and the reaction was continued at 80°C under N2atmosphere for 6 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried at 70°C, and the fluorescence intensity was measured.

[0053] Comparative Example 3:

[0054] To a 100 ml three-necked flask, polyetheramine (Mn=2000, 4 g), HDI (0.706 g), DBTDL (0.02 g) were added as solvent DMAC, and the reaction was carried out at 80°C under N2atmosphere for 2 h with mechanical stirring to obtain a colorless viscous solution, which was a prepolymer. After obtaining the prepolymer, 1,5-dihydroxynaphthalene (0.32 g) was added, and the reaction was continued at 80°C under N2atmosphere for 6 h. After the reaction was completed, a viscous DMAC solution of polyurea was obtained, which was poured into a mold and dried at 70°C, and the fluorescence intensity was measured.

[0055] Comparative Example 4:

[0056] Using DMAC as solvent, polyetheramine (Mn = 2000, 4 g), HDI (0.706 g), and DBTDL (0.02 g) were added to a 100 mL three-necked flask. The mixture was mechanically stirred for 2 h at 80 °C under a N2 atmosphere to obtain a colorless, viscous solution, which was the prepolymer. After obtaining the prepolymer, 1,5-diaminonaphthalene (0.316 g) was added, and the reaction was continued for 6 h at 80 °C under a N2 atmosphere. After the reaction was completed, a viscous polyurea DMAC solution was obtained, which was poured into a mold, dried at 70 °C, and its fluorescence intensity was measured.

[0057] (Comparative Examples 2, 3, and 4 were analyzed only for fluorescence intensity to compare the effect of substituents on the naphthalene ring on fluorescence intensity; their mechanical properties were not investigated.)

[0058] Table 1 shows a comparison of the mechanical properties of different embodiments and comparative examples, demonstrating that the high-toughness NDI-based fluorescent polyurea synthesized in this invention has ultra-high toughness and excellent elongation at break.

[0059] Table 1

[0060]

[0061]

[0062] like Figure 1 As shown, NSPUA (Comparative Example 1), NSPUA-IP1 (Example 1), NSPUA-IP2 (Example 2), and NSPUA-IP3 (Example 3) represent the proportions of no crosslinking agent and crosslinking agent added, respectively (the larger the number, the larger the proportion). With the increase of crosslinking agent content, the degree of crosslinking increases, and the toughness is greatly improved.

[0063] like Figure 2 As shown, with the increase of crosslinking degree, the "movement" of naphthalene ring is restricted, nonradiative transitions are weakened, radiative transitions are enhanced, and fluorescence intensity increases.

[0064] like Figure 3 As shown, NSPUA-IP3 (Example 3) was immersed in solutions with different pH values ​​for 24 hours, and its fluorescence intensity was measured. It can be seen that the fluorescence intensity changed significantly. This is because different acid and alkaline environments changed the existence form of the substituents on the naphthalene ring and affected the electron cloud density of the naphthalene ring, thus changing the fluorescence intensity of the material.

[0065] Figure 4As shown, the NN (comparative example 4) represents the system in which all urea groups, the NO (comparative example 3) represents the system in which the substituent on the naphthalene ring is a urethane bond, and there is a urea group in the system, the OO (comparative example 2) represents the system in which all are urethane bonds. The fluorescence intensity of the system in which the substituent on the naphthalene ring is a urea group and all are urea groups is much greater than that of the system in which there is a urethane bond. The hydrogen bond energy formed between the urea groups is higher than that of the hydrogen bond between the urethane bonds, and the distance is closer. The more the range of the "movement" of the naphthalene ring is limited, the less the non-radiative transition is, the radiative transition is enhanced, and the fluorescence intensity is enhanced.

[0066] The above fluorescence characteristics make the material can be applied to marking, display and other fields.

[0067] The above only for the preferred embodiments of the present application, and not for limiting the present application, for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of high-toughness NDI-based fluorescent polyurea, characterized by, Comprise: naphthalene diisocyanate NDI is reacted with polyether amine to obtain an isocyanate-terminated prepolymer; The isocyanate-terminated prepolymer is chain-extended with tetraethylenepentamine TEPA, and after the reaction is completed, diisocyanate is added to continue the reaction, and the high-toughness NDI-based fluorescent polyurea is obtained; The polyether amine is polyether amine D-2000.

2. The process for the preparation of high-toughness NDI-based fluorescent polyurea according to claim 1, characterized in that, The molar ratio of the NDI to the polyether amine is 1:0.3-1.

3. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1 wherein, The temperature for the reaction of the NDI with the polyether amine is 0-60°C.

4. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1, wherein, The temperature for the chain extension reaction is room temperature.

5. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1, wherein, The molar ratio of the polyether amine to the TEPA is 1:0.3-1.

6. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1, wherein, The reaction temperature of the diisocyanate with the secondary amine is 50-100°C.

7. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1, wherein, The molar ratio of the TEPA to the diisocyanate is 1:0.3-1.

6.

8. The process for the preparation of high-toughness NDI based fluorescent polyurea as claimed in claim 1 wherein, The diisocyanate is selected from one of isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI, and toluene diisocyanate TDI.

9. The high-toughness NDI-based fluorescent polyurea prepared by the method of any one of claims 1-8.

10. The high-toughness NDI-based fluorescent polyurea of claim 9 in the field of information storage and encryption, information marking and display.

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